The present invention relates to the treatment of obstructions in a blood vessel, and particularly the elimination of such obstructions by chemical dissolution.
The formation of a blood clot in the cardiovascular system usually requires prompt medical intervention, and this is particularly true in the case of arterial blood clots, most particularly those in a coronary artery, since such clots can be life threatening. Obstructions formed of other materials, such as plaque and fibrin, can also require medical intervention.
Various techniques for removing such obstructions are known, these techniques generally involving surgical intervention or the delivery of a dissolution agent, e.g., a thrombolytic agent.
In principle, the use of a thrombolytic agent offers the advantage of avoiding the physical trauma associated with surgical intervention. However, the techniques typically employed to deliver thrombolytic agent to the site of a clot are somewhat complex and/or require the introduction of a considerable quantity of thrombolytic agent into the blood stream in view of the fact that such agent is entrained in the blood stream and thus carried away from the site of the clot, unless the clot is completely blocking the vessel. Since thrombolytic agents are foreign substances to the patient's body, the larger the quantity of such agent introduced into the blood stream, the greater the danger of adverse side effects and the greater the cost. In addition, if large quantities of agent are introduced into the blood stream, the result could be that subsequent surgical intervention which might otherwise be indicated could not be performed. Similar considerations apply to other types of dissolution agents.
U.S. Pat. No. 4,423,725, which issued to O. E. Baran on Jan. 3, 1984, describes an intervention device composed of a catheter having a blood flow lumen, a chemical delivery lumen and a suction lumen, associated with two annular cuffs which are inflatable to isolate a blood vessel region containing an obstruction. This patent discloses the treatment of blood vessel obstructions by balloon angioplasty followed by the application of anticoagulant drugs or cholesterol diluting drugs.
There is frequently a need to remove obstructions from blood vessels having relatively small diameters. In these situations, a device must be provided to perform all of the following requisite functions: maintaining blood flow past the obstruction, while blocking the vessel in order to retain the dissolving chemical; supplying inflation air to the blocking balloon; delivering a dissolving chemical; and suctioning the material forming the blockage after it has been dissolved or broken up. Because of the difficulty of providing a sufficiently small device capable of performing all of these functions, it has not been possible to chemically treat many life-threatening blood vessel blockages.